1. Technical Field
The present invention relates to a plastic polarized lens and a method of producing the same.
2. Related Art
A polarized lens can prevent transmission of reflected light. Therefore, it is used for protecting eyes by intercepting a strong reflected light in outdoor such as in a skiing ground or in fishing, and for securing safety in driving a car by intercepting a reflected light from a car running in the opposite direction.
For a plastic polarized lens, two kinds of polarized lens are proposed, namely, a polarized lens with a polarized film laid on the surface of the lens material, and a sandwich structured polarized lens with a polarized film within the lens. The polarized lens with a polarized film laid on the surface of the lens material (for example, Japanese Patent Application Laid-Open No. H09-258009 (Patent Document 1)) can make the thickness of the lens thin, but has a serious disadvantage that the polarized film is liable to be peeled off from the lens material during a periphery grinding process (a process of grinding periphery of the lens to fit in a predetermined shape).
A resin used for a polarized film composing a polarized lens has been essentially limited so far to polyvinyl alcohol. The polarized film is produced by a uniaxial extension of polyvinyl alcohol film after adding iodine or a dichroic dye to make a film having molecular orientation in uniaxial direction. A method of producing a polarized lens composed of a polarized polyvinyl alcohol film is disclosed, for example, in the WO 04/099859 (Patent Document 2).
However, the polarized lens produced by using a polarized polyvinyl alcohol film has shortcomings of gradual penetration of water from the rim of the lens causing deterioration from the periphery to the center of the lens with time or due to the surrounding environment.
In order to improve above-mentioned shortcomings, the pamphlet of WO 02/073291 (Patent Document 3) proposed a polarized lens using a lens material containing impact-resistant polyurethane resin obtained from diamine and isocyanate-prepolymer, and a polarized film containing polyethylene terephthalate.
However, this polarized lens has a disadvantage that the polarized film contained in the lens is clearly visible from outside which gives an uncomfortable feeling to a person who wears the eyeglasses containing this lens. Furthermore, as the composition of the mixture of diamine and isocyanate prepolymer has a high viscosity and a short pot life, injection of the composition to a lens mold with a fixed polarized film therein is troublesome, and production of a thin lens was particularly difficult.
Therefore, in the conventional plastic polarized lens, there has been a demand for a plastic polarized lens having reduced occurrence of peeling-off of the polarized film during a downstream process of grinding the periphery of the lens and excellent water-resistance, giving less uncomfortable feeling on wearing, and is capable of producing a thin product.